Young Jeezy is currently behind bars for possession of an assault rifle … and TMZ has learned the weapon turned up during the investigation into the deadly shooting at Wiz Khalifa’s concert Friday night.

Someone got murdered during the “Under The Influence Of Music” tour stop in Mountain View, CA. So cops did a search and found a gun they believe belongs to Jeezy. His bail is set at a million dollars. Hopefully this is figured out quickly, Young Jeezy’s “Seen It All” drops September 2nd.